U.S. Pat. No. 4,979,534 to Johnson et al. disclosed a windproof umbrella having a lower canopy with vent holes and an upper canopy in covering relation to the vent holes to provide air escape during high winds so as to prevent inversion of the umbrella.
Johnson's prior art is illustrated in FIG. 22, in which the upper canopy (36) is resiliently secured to the tips (28) by elastic straps (48), and the lower canopy (20) is secured on the ribs (18) which are pivotally connected with the struts (16) at points (P) and the runner held on the shaft. Upon wind (W) blowing through the vent holes 34, the air will escape through the aperture between the upper canopy (36) and the lower canopy (20) by forcibly stretching the elastic straps (48). Since the lower (outer) end portion of each strap (48) is distantly separated from the pivotal connection point (P), a great arm of force as effected by strong or high winds will exert a great moment acting upon the pivotal connection points (P) to cause breaking from such points (P), thereby easily breaking and damaging the ribs of the umbrella of the prior art.
The present inventor has found the drawbacks of the conventional windproof umbrella and invented the present windproof umbrella which can be reliably controlled.